Complete response to ethnylestradiol prolonged for almost two years in patients with castration-resistant prostate cancer

An 80-year-old man with an elevated prostate-specific antigen (PSA) level of 120 ng/mL) presented to the hospital in February 2011. A prostate needle biopsy was performed, and pathological examination revealed prostatic adenocarcinoma. The Gleason score was 4+5=9. Computed tomography revealed metastases of the pelvic lymph nodes. Combined androgen blockade was started. The PSA concentration decreased to 1.68 ng/mL, but started increasing again in August 2012 to 6.08 ng/mL. Although bicalutamide was discontinued due to antiandrogen withdrawal syndrome, the PSA concentration increased even more. The PSA concentration reached 21.62 ng/mL in September 2012, at which time ethnylestradiol was started. The PSA concentration decreased again and has remained below the limit of sensitivity for almost 2 years. To our knowledge, this is first case report describing a complete response to ethnylestradiol that lasted for almost 2 years in a patient with castration-resistant prostate cancer.